Multi-emitter lighting system with calculated drive

ABSTRACT

Systems and methods permit use of efficient solid state emitters for broad spectrum continuous spectrum lighting defined by illumination data. The illumination data, which can be sold as a commercial product, can be recorded or authored and include spectral, temporal, and spatial information. A lighting fixture can use information such as the illumination data, emitter age, temperature, and calibration data to calculate drive levels as needed to control intensities of individual emitters and thereby produce desired patterns of spectral content and time variation.

CROSS-REFERENCE TO RELATED APPLICATIONS

This patent document is a divisional and claims benefit of the earlierpriority date of U.S. patent application Ser. No. 14/682,391, filed Apr.9, 2015, which claims the priority of U.S. patent application Ser. No.13/892,042, filed May 10, 2013, now U.S. Pat. No. 9,028,094, whichclaims the priority of U.S. patent application Ser. No. 13/105,837,filed May 11, 2011, now U.S. Pat. No. 8,469,547, which claims thepriority of U.S. patent application Ser. No. 12/215,463, filed Jun. 26,2008, now U.S. Pat. No. 8,021,021, all of which are hereby incorporatedby reference in their entirety.

BACKGROUND

The portion of the electromagnetic spectrum with wavelengths betweenabout 350 nm and 750 nm, which includes visible light, is useful formany purposes. For example, these wavelengths enable human vision andphotosynthesis by providing enough energy to do useful work inbiological systems but not so much energy as to destroy the biologicalsystems. The sun produces vast amounts of radiation in this spectralrange and the earth's atmosphere allows transmission of thesewavelengths to the surface. Other natural light sources such as fire andlightning as well as man-made sources such as incandescent, fluorescent,and solid state lighting also produce electromagnetic radiation or lightin this spectral range.

Lighting from the sun is arguably the “gold standard” of illuminationsince humans are adapted to live in solar illumination. For the sun, thequantity of light varies with time from darkness to blinding. The sunhas both intense collimated light from a small area (the solar disk) andsubdued diffuse light from a large area (blue sky). The spectraldistribution, location, and direction of light from the sun also changein a relatively consistent way as the sun moves across the sky. Thesesolar lighting patterns affect many biological processes such as thehuman wake-sleep cycle and plant and animal lifecycles, which are ofteninfluenced by solar patterns.

The dynamic variation in illumination from man-made light sources isgenerally much smaller than the dynamic variation in the illuminationfrom the sun. In the cases of candles, incandescent bulbs, fluorescenttubes, and discharge lamps, the spectrum and to a large degree theamount of light provided are fixed at the time of installation. Somedimming and spectral change are possible over a limited range, butillumination from the vast majority of these lighting systems is static.In addition, where dimming or spectral modifications are possible, thedimming often decreases the energy efficiency of the light source, andspectral modifications, which are conventionally achieved with opticalfilters, can be very wasteful of energy. Other light qualities likelocation, direction, and beam divergence are also fixed in mostinstallations. However, the value of human vision is so great that thisstatic, inflexible illumination is acceptable in many cases.

Lighting systems and methods are desired that provide greaterflexibility and dynamic qualities.

SUMMARY

In accordance with an aspect of the invention, lighting systems andmethods improve several aspects of light quality over conventionalapproaches. In particular, illumination data can define continuous broadspectrum lighting that can be produced using a player and luminairescontaining multiple solid state emitters such as LEDs. The illuminationdata, which may be recorded from an existing natural or manmade lightingenvironment or authored, can include spectral, temporal, and spatialinformation defining the qualities of the light produced. Theintensities of individual emitters in the luminaires can be controlledthrough a combination of pulse width modulation (PWM) and amplitudemodulation (AM) of drive currents. The combination of PWM and AM permitsfine tuning of the spectrum of emissions and creation of free spaceoptical data channels.

In accordance with one specific embodiment of the invention, a processproduces illumination data to represent a desirable spectraldistribution and uses the illumination data to control operation of alight source containing multiple emitters such as LEDs with differentpeak wavelength emissions. In particular, the light source operates theemitters so that respective intensities of light from the emitters aredetermined from the illumination data and a combination of therespective intensities of the emitters produces the desired spectraldistribution. The illumination data can be produced by a variety oftechniques ranging from recording the illumination characteristics in aspecific environment to authoring the illumination data from scratch toachieve a desired function or aesthetic effect.

In accordance with another specific embodiment of the invention, asystem includes one or more light sources and a player connected to thelight source or sources. Each light source includes multiple emitterssuch as LEDs with each of the emitters having an emission spectrum thatdiffers from the emission spectra of the other emitters. The player isconnected to independently control the intensity of light emitted fromeach of the emitters. The player is further capable of accessingillumination data representing a spectral distribution and usesillumination data to determine respective intensities of emissions fromthe emitters required to produce the illumination represented by theillumination data.

In accordance with yet another embodiment of the invention, a businessmethod includes creating illumination data that represents informationincluding the spectral distribution of a desired illumination. Theillumination data can be sold in a file format that can be playedthrough a lighting system to reproduce the desired illumination.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a chromaticity diagram illustrating the apparent color oflight sources containing a few narrow band emitters.

FIG. 2 shows a luminaire in accordance with an embodiment of theinvention using narrow band light sources to provide illumination havinga broad wavelength range.

FIG. 3A shows a programmable spectral distribution from a light sourcein accordance with an embodiment of the invention.

FIG. 3B shows the spectra of phosphor converted LEDs that can be usedwith the spectra of direct LED emissions to produce a programmablespectral distribution.

FIG. 4 illustrates a system in accordance with an embodiment of theinvention for illuminating a room.

FIG. 5 illustrates a system in accordance with an embodiment of theinvention for recording illumination data.

FIG. 6 is a flow diagram illustrating a business method for sellingillumination data in accordance with an embodiment of the invention.

Use of the same reference symbols in different figures indicates similaror identical items.

DETAILED DESCRIPTION

The emergence of solid state light sources, most notably LEDs (lightemitting diodes) has provided much longer lasting, more robust, and moreenergy-efficient alternatives to conventional vacuum and combustiblelight sources. However, while most conventional light sources are broadspectrum (e.g., white light) emitters, LEDs are generally narrowspectrum emitters that intrinsically produce colored light with arelatively narrow distribution of wavelengths. Since white light isoften preferred, LED systems using a blue LED and yellow phosphor havebeen developed that appear white. However, the light from conventionalLED systems is generally less than ideal for many lighting applications.In accordance with an aspect of the present invention, multiple LEDswith different colors or emission peaks can be combined to produceillumination with a desired spectrum, rather than simply providing theappearance of a specific color such as white.

The apparent color of a light source can be roughly determined using achromaticity diagram such as an International Commission on Illumination(CIE) chromaticity diagram 100 as shown in FIG. 1. Chromaticity diagram100 has a border 110 that corresponds to spectral colors in the visiblespectrum, i.e., monochromatic light with wavelengths between about 380nm and about 700 nm. Points inside border 110 in chromaticity diagram100 correspond to colors perceived by the human eye in response tocombinations of spectral colors. In particular, a point or region 120corresponds to the color white, which can be produced using manydifferent combinations of spectral colors. For example, white light canbe produced by a black body that is heated to the correct temperature.In FIG. 1, a curve 125 represents the apparent color of blackbodyradiation over a range of temperatures of an ideal blackbody. As is wellknown, a blackbody begins to glow with a reddish color at about 1500° K,changes through orange and yellow as the temperature of the blackbodyrises, and appears whitish at temperatures between about 4000 and 6000°K. Incandescent lights generally produce light that appears whitethrough electrical heating of a filament, and the light from anincandescent bulb can be similar to blackbody radiation.

The spectrum of blackbody radiation is a continuous spectrum, but theappearance of white can also be achieved using just two spectral colors.In particular, if a line connecting two points in chromaticity diagram100 passes through the region 120 corresponding to white, two lightsources with colors corresponding to those points when combined with theproper intensity ratio appear white. FIG. 1 specifically illustratesthat a line 130 connecting points 132 and 134 respectively correspondingto spectral colors blue and yellow passes through region 120, and acombination of the blue and yellow light will appear white if the ratioof the intensities of the two colors corresponds to a point in region120. A line 140 also crosses region 120 showing that other colors, e.g.,cyan (point 142) and red (point 144) could alternatively be used togenerate the appearance of white. However, a two color system is notvery flexible as a light source. In particular, a two color light systemcan only produce the appearance of colors on lines connecting thecorresponding points in a chromaticity diagram. Further, illuminationusing two color sources cannot provide the full spectral content of anatural light source such as the sun, and therefore the lighting suffersthe problem of metamerism, as described further below.

Producing the sensation of a range of colors, for example, for a colorvideo display, generally requires illumination with at least threecolors. Most commonly the three colors are red, green, and blue, forexample, points 152, 154, and 156 in chromaticity diagram 100. Varyingthe ratios of the intensity of these primary colors can generate anycolor (including white) within a triangle 150 having points 152, 154,and 156 as vertices as shown on diagram 100. Most video displays (TV,computer, stadium screen, etc.) use variation of the relativeintensities of red, green, and blue light to produce the sensation of arelatively full range of colors. The sensation of different colors canbe achieved because human eyes normally have three types of cones, andthe respective cones are most sensitive to red, green, and blue light.Since LEDs can be made in red, green, and blue, LED displays using threecolors can produce color changeable or static colored light fordisplays, accent, or illumination.

While a three primary color system does a good job of creating thesensation of many colors, such a system does not come close toaccurately representing the continuous spectrum and specific spectralpower distributions of broad spectrum sources such as the sun, fire, oran incandescent bulb. Accordingly, a three primary color system is notcompletely satisfactory as a source of illumination, particularly forobjects with significant reflectance in between or beyond the threeprimary colors emitted. Differences in an illumination spectrumgenerally can change the appearance of objects, and most people wouldprefer sunlight or at least continuous spectrum sources to look at anobject for the best viewing of color. Another benefit of continuousspectrum sources, particularly the sun, over illumination using threeprimary colors is the presence of short wavelength light that can causefluorescence in the objects illuminated. The fluorescence helps givesparkle to objects that can otherwise look dull under poor lighting.

As previously alluded, a situation known as metamerism exists where twoobjects with different spectral characteristics look the same underillumination by one light source but not under illumination by anotherlight source. This situation can sometimes be avoided or remedied bytailoring the spectral characteristics of an object during manufacturingor by limiting the spectral characteristics of the lighting of theobject. However, these options are often not available or producesub-optimal results, and an observer can be left frustrated that objectsappear to have different colors in different lighting. An example ofthis occurs when a customer buys black pants and an apparently blackblazer in a store with fluorescent lighting only to find later that theblazer is actually navy blue when viewed in sunlight.

Broad spectrum lighting may have benefits in addition to improving theapparent color of objects. Cones, which are eye cells that resolvecolors, occupy an important but small region of the human eye, but theeye also contain rods that extend over a larger portion of the retina.The rods are important for peripheral vision and vision in low lighting.Rods have a scotopic curve that peaks at a light wavelength of about 507nm. Human eyes also have sensors that are in a layer of ganglion cellsthat cover most of the inside surface of the eye. These sensors cansense non-visual information and are believed to be responsible for theregulation of various bodily functions such as the sleep/wake cycle andhormone production. The peak sensitivity for these cells occur about 480nm, which is between blue and green and roughly the color of blue sky.The wavelengths of peak sensitivities of these cells are not normally animportant region of the spectrum emitted by traditional LED lighting.Fixtures that produce light in the correct spectral regions can thushave biological benefits and improve vision under lower lightingconditions. A programmable, continuous spectrum light source can addressthese and other conditions that are important for a given situation.

The color anomalies and failure of lighting to provide light havingwavelengths corresponding to peak sensitivities of specific biologicalsystems can be virtually eliminated through use of many narrow spectrumsources that collectively provide illumination that continuously coversan extended portion of the visible spectrum or beyond. FIG. 2illustrates a luminaire 200 in accordance with an embodiment of theinvention containing multiple types of LEDs 210-1 to 210-N. Thedifferent types of LEDs 210-1 to 210-N have different emission spectraand collectively can be configured and operated to produce a recorded orauthored spectral distribution over a broad range of wavelengths, e.g.,a range that covers most of the visible spectrum and that may extend toultraviolet or infrared wavelengths. The number N of types of LEDs 210-1to 210-N required to cover the desired range of wavelengths generallydepends on the range and the widths of the emitted spectra of LEDs 210-1to 210-N. In an exemplary embodiment, LEDs 210-1 to 210-N have differentcolors (e.g., from 5 to 50 different colors) with peak emissionwavelengths in a range from about 400 nm to about 700 nm, and the peakemission wavelengths of LEDs 210-1 to 210-N can be separated by steps ofabout 5 nm to about 50 nm to continuously cover the visible spectrumwhen individual LED spectra have FWHM of about 15 to 35 nm. A diffuser215, which is an optical device such as a frosted plate of a transparentmaterial, can be used to mix light from the LEDs 210-1 to 210-N toprovide more spatially uniform lighting that combines light from allLEDs 210-1 to 210-N. Additionally, LEDs 210-1 to 210-N of the same typecan be scattered in different locations within an array of LEDs 210-1 to210-N for better spatial uniformity of the spectrum of emitted light.

LEDs having different peak emission wavelengths can be produced usingdifferent materials or structures and would normally be provided onseparate chips. However, the part of the spectrum between about 540 nmand 590 nm is inefficient for direct emission from current LEDs becausethis wavelength range is near the extremes of the two dominant LEDmaterial systems, InGaN (540 nm) and AlInGaP (590 nm). Phosphors (notshown) can be added to one or more LEDs 210-1 to 210-N to convert directLED emissions to the desired wavelengths through fluorescence. Adisadvantage to the phosphor conversion when compared to direct LEDemissions is degraded spectral resolution. LED phosphor emissionsgenerally have much broader spectral profiles than do the directemissions from an LED, and the emitted spectrum from the LED-phosphorcombination may contain an emission peak corresponding to fluorescenceand a second peak from the intrinsic emitted wavelength of the LED.These effects could limit the ability to tune the overall spectrum oflight emitted from luminaire 200. Even so, phosphor converted LEDs arelikely to have an important role in continuous-spectrum products.

A consequence of using LEDs of wavelengths across the visible spectrummay be a loss of energy efficiency because current LED technologyproduces light of some wavelengths less efficiently. The number of LEDsof each type (i.e., having the same or very similar peak emissionwavelengths) may differ to enable a more uniform maximum intensityacross the spectrum. For example, the number of LEDs of a specific typein luminaire 200 may be selected, so that the LEDs of each type have thesame combined maximum intensity. Use of less efficient LEDs reducesoverall energy efficiency of luminaire 200 but may be unavoidable whenaccuracy of the final spectrum is the priority. Alternatively, more LEDsof the most energy efficient type or types can be included in luminaire200 for use when energy efficiency is preferred over spectral accuracy,for example, for outdoor lights that are on much of the time. Luminaire200 may also employ light sources that have broader spectra in additionto or in place of LEDs with narrow spectra that cover the same range ofwavelengths. In particular, when the available LEDs are less efficientat producing light with specific wavelengths, luminaire 200 can includeLEDs with phosphors that fluoresce to produce light with the wavelengthsthat are less efficiently produced by direct emission from LEDs. Thebroad spectrum sources may be used when spectral resolution is lessimportant than energy efficacy.

In addition to LEDs 210-1 to 210-N, luminaire 200 contains a fixturecontroller 220 that operates a programmable LED 230 driver toindividually adjust the intensity of light emitted from each of LEDs210-1 to 210-N. In particular, the intensities emitted from LEDs 210-1to 210-N can be adjusted to provide lighting that approximates anydesired spectral power distribution over the range of wavelengths ofLEDs 210-1 to 210-N. FIG. 3A illustrates an example of a spectraldistribution 300 that is the sum of narrow band distributions 310-1 to310-N respectively having characteristic peak wavelengths λ₁ to λ_(N) ofrespective LEDs 210-1 to 210-N. The illustrated spectral distribution300 corresponds to white light having roughly equal intensities of lightfor all wavelengths between about 350 nm and 750 nm. However, peakintensities s I₁ to I_(N) of narrow band spectral distributions 310-1 to310-N for LEDs 210-1 to 210-N have magnitudes under the control ofdriver 230 of FIG. 2. Fixture 200 can thus reproduce a desired spectrumby separately adjusting each of intensities I₁ to I_(N). The accuracywith which a spectral distribution can be reproduced generally dependson the number of different peak wavelengths λ₁ to λ_(N), the widths ofthe emission spectra of the types of LEDs 210-1 to 210-N, and thedynamic range of intensity of each of LEDs 210-1 to 210-N. To optimizespectral accuracy, a large number of (e.g., on the order of 20 to 50)types of LEDs 210-1 to 210-N are desired with each type having adifferent wavelength for peak emissions. The widths of the emissionspectra of each type should be as narrow as possible while stilloverlapping with the emission spectra of other LEDs 210-1 to 210-N ofother types. However, light sources of phosphor converted LEDs whichhave wider distributions, such as the spectral distributions 320-1 to320-N shown in FIG. 3B, can be used when the accuracy of the reproducedspectrum is less important or when light sources having wider spectrumare more efficient at producing light with a desired wavelength.

Driver 230 can generally dim each of LEDs 210-1 to 210-N to almost anydesired extent by pulse width modulation (PWM) and/or amplitudemodulation (AM) of the respective drive currents of the LEDs 210-1 to210-N. In one embodiment of the invention, independent drive currentsrespectively control the intensities of LEDs 210-1 to 210-N, and LEDdriver 230 modulates the amplitudes of the drive currents to the LEDs210-1 to 210-N and alters the on-time of the drive currents for both PWMand AM control. The use of both PWM and AM has advantages over justusing one or the other. In particular, a desired overall dynamic rangeof illumination intensity for luminaire 200 may be 100,000:1 or greater.A range of AM between 10:1 and 1000:1 would thus be desirable. If AM isnot used in control of drive currents in luminaire 200, a largemagnitude current would be needed to achieve the desired maximum lumens,and dimming can only be accomplished with shorter pulses of drivecurrent. Operating at near darkness illuminations then requires shortpulses with fast edges, generating more noise (EMI) which has to beabated in some way. Further, the efficiency of an LED is often inverselyproportional to the drive current, and use of short high current pulsesdoes not provide maximum energy efficiency. This is particularly true ofthe InGaN materials used for short to mid wavelengths and phosphorconverted white. For example, a reduction by a factor of 10 in the drivecurrent to an InGaN-based LED can result in a 70% increase inefficiency. Energy lost as heat (or I²R losses) in driver 230 and wiringalso goes up as the drive current goes up. The ability to adjust themagnitude of the drive current can avoid these problems with using PWMalone, and combining AM and PWM may also provide a way of tuning theemission spectrum of each LED 210-1 to 210-N because the peak emissionwavelength of an LED often has at least some correlation to theamplitude of the drive current.

Uses of PWM or AM are not limited to static and relatively slow lightingeffects. LEDs can be turned on and off very rapidly, much faster thanthe eye or even many machines could detect. The rapid switching speed ofLEDs 210-1 to 210-N could be exploited to transmit data and in manycases at the same time as static or average illumination is being usedfor other purposes. Further with the multiplicity of differentwavelength sources, each LED 210-1 to 210-N could operate fortransmission of a separate data channel, which could greatly increasethe available data bandwidth.

Luminaire 200 of FIG. 2 used as described above can accurately reproduceor approximate the spectral and brightness characteristics of manydifferent light sources or produce lighting according to a patterncreated by an author or engineer. In one embodiment of the invention,luminaire 200 uses illumination data to define specific illuminationthat luminaire 200 produces. The illumination data can be input intoluminaire 200 through a communication interface 250 or stored in astorage system 260. In an exemplary embodiment, communication interface250 connects luminaire 200 to a network that may include similarluminaires or control devices and can further be part of a userinterface that allows a user to control luminaire 200, for example, toselect active illumination data for operation of luminaire 200. Storagesystem 260 in luminaire 200 can be used to store illumination data andexecutable code for fixture controller 220 and may be any type of systemcapable of storing information. Such systems include but are not limitedto volatile or non-volatile IC memory such as DRAM or Flash memory andreaders for removable media such as magnetic disks, optical disks, orFlash drives.

FIG. 2 illustrates storage 260 as containing two types of illuminationdata including presets 262 and user files 264. Presets 262 are factoryinstalled illumination data files that represent default lighting orlighting that would be useful to a wide number of users. The presetsmight include, for example, the spectra of common natural light sourcesuch as the sun at noon on a cloudless summer day or a full moon, thespectra of flame based light sources such as candles or a camp fire, thespectra of common electrical light sources such as incandescent orfluorescent lights, and the spectra that provide luminaire 200 withoptimal energy efficiency for human vision over a range of differentintensities. User files 264 are illumination data that a user has chosento store in luminaire 200. User files 264 can include illumination dataof the same types as mentioned for the presets but additionally includeillumination data that are of particular interest for a specific user.For example, an individual may load into storage 260 illumination datathat provides light having spectral content and time variation that isoptimized for their sleep cycle or the sleep cycle of their child. Aresearcher may load into storage 260 illumination data that createlighting that provides the desired spectral content for an experiment orlighting that optimizes the growth of particular plants or organisms.

There are many different types of lighting that can be represented byillumination data files that can be stored as presets or user data instorage 260. To list a few examples, luminaire 200 can reproduce orapproximate the spectrum of light from a natural source such as the sunor the moon as it would appear on specific days, times, and locations.Illumination data can represent light with a spectrum mimicking aconventional manmade light source such as an incandescent light of anyof a variety of types, a fluorescent light, a gas flame, a candle, anoil lamp, a kerosene lantern, an arc-lamp, or a limelight, or representlight with a spectrum having a specific utility such as a black light, abug light, a film-safe light, a grow lamp, or colored lightcorresponding to any desired filter effect. All of these different typesof lighting which may be represented by illumination data can bereproduced by luminaire 200. Luminaire 200 can also produce light havinga spectrum of a light source that does not normally exist such as 5000°K halogen light, which cannot be easily made because the filament wouldmelt. Also, as mentioned above, the 200 to provide optimal energyefficiency, for example, to change the shape of the spectrum ofluminaire 200 with brightness level for best human vision or otheruseful purpose per amount of energy consumed.

Illumination data could have a variety of different file formatssuitable for representing the desired lighting information. A staticspectral distribution, for example, may be simply represented using aset of samples corresponding to a set of different wavelengths of light.Alternatively, a static spectral distribution could be represented bythe coefficients of a particular transform, e.g., Fourier transform, ofthe spectral distribution. Further information in the illumination datacould represent how the spectral distribution changes with time orabsolute intensity. The illumination data could further includepositional or directional information to indicate spatial variations inthe spectrum and intensity of lighting, particularly when luminaire 200is used with other similar lighting fixtures to illuminate a room orother environment.

Fixture controller 220 decodes the illumination data that a user selectsfor operation of luminaire 200 and programs driver 230 as needed tocause LEDs 210-1 to 210-N to produce the lighting called for in theillumination data. In general, fixture controller 220 can employ datafrom multiple sources in order to determine the correct programming ofdriver 230. For example, fixture controller 220 can interpolate betweensamples provided in the active illumination data when the peakwavelengths emitted from LEDs 210-1 to 210-N differ from wavelengthsrepresented in the selected illumination data. Calibration data 266,which may be factory set in storage system 260, can indicate the peakemitted wavelengths respectively measured from LEDs 210-1 to 210-N aswell as other LED performance data such as emission intensity dependenceon drive current, temperature, or other factors. For each LED, fixturecontroller 220 can then use calibration data 266 and temperature datafrom a temperature sensor 270 to determine the drive signal needed forthat LED to produce the required contribution to the spectraldistribution represented in the selected illumination data. A lightsensor 280 can be employed to monitor the emitted light from LEDs 210-1to 210-N to allow fixture controller 220 to adapt the calculation of therequired drive signals according to changes in performance that occur asluminaire 200 ages or is used.

Luminaire 200, which can produce virtually any illumination spectralpower distributions within the power limits of the LEDs 210-1 to 210-N,can be used with other similar luminaires to produce desired spatialpattern in lighting. The spatial pattern of the lighting may be subjectto temporal variations in the same way the spectral content may vary.For example, lighting that reproduces the path of solar illuminationfrom dawn to dusk would include spatial, spectral, and intensityvariations over the course of a day. A system implementing desiredspatial, spectral, and intensity patterns for lighting could beemployed, for example, in scene lighting or home lighting.

FIG. 4 illustrates a room 400 containing a lighting system in accordancewith an embodiment of the invention providing lighting with spatialvariations. Room 400 includes multiple light sources 410, 420, and 430.Each light source 410, 420, or 430 can be a flexible luminaire such asluminaire 200 of FIG. 2 and therefore be capable of producing lighthaving a programmable spectral profile. A lighting control or playersystem 450 is in communication with light sources 410, 420, and 430 andmay be a separate unit as illustrated in FIG. 4 or may be physicallyincorporated in one or more of luminaires 410, 420, and 430. Playersystem 450 can include specially designed hardware or a general purposecomputer executing software to implement the desired lighting functions.

Luminaires 410, 420, and 430 can act as a network under control ofplayer system 450 to provide room lighting with the desired spectral,temporal, and spatial distribution. A variety of physical and logicalarrangements of multiple luminaires 410, 420, and 430 are possible. Forexample, each luminaire 410, 420, and 430 could have a network address,all luminaires 410, 420, and 430 could be connected in a serial fashion,or luminaires 410, 420, and 430 could be configured and addressed inrows and columns to provide an area with overhead lighting. Preferably,the configuration used allows player system 450 independentcommunications with each luminaire 410, 420, or 430.

During setup or operation of lighting in room 400, player system 450 canpoll the characteristics of each particular luminaire 410, 420, or 430to determine light source characteristics, which may include static anddynamic information. The static information could, for example, includethe positions of luminaires 410, 420, and 430 and the number of colorsand type of emitters in each of luminaires 410, 420, and 430. Thedynamic information can include the temperatures, ages, and number ofluminaires 410, 420, and 430. Player system 450 can further includesensors capable of measuring the spectral distribution of light at oneor more points in room 400. Based on the measured light or thedetermined characteristics of luminaires 410, 420, and 430 and theselected illumination data, player system 450 selects spectraldistributions for respective luminaires 410, 420, and 430, and playersystem 450 or luminaires 410, 420, and 430 can calculate the drivecurrents of the emitters in luminaires 410, 420, and 430 needed toproduce the desired lighting in room 400.

Player system 450 is capable of executing complex lighting programs thatinclude specific spectral and spatial distributions and time variationsof the spectral and spatial lighting in room 400. For example, thespatial and spectral information in an illumination data file couldmimic large scale illumination sources, such as the sky, from contentspecifically recorded for playback in lighting systems. Lighting in room400 could thus reproduce the spectral distribution of diffuse lightingfrom the sky recorded from a specific location and time of the day andyear. Further, lighting in room 400 could additionally mimic timevariations in the spectral distribution of the sky over a day or seasonin real time or at a compressed or extended time scale. A brightlocalized lighting associated with the sun could be super imposed overthe sky light program. Player system 450 could alternatively be switchedto reproduce lighting in room 400 that mimics the flickering andspectral characteristics of a camp fire or candle light, the light fromincandescent bulbs, or even a lightning strike. More generally, playersystem 450 can be operated to produce any lighting that may berepresented in an illumination data file recorded or authored for thatpurpose.

In accordance with a further aspect of the invention, a recorder systemcan be employed to capture the spectral, temporal, and directionalcharacteristics of an existing lighting environment for reproduction inthe lighting system of FIG. 2 or 4. FIG. 5 illustrates a simplerecording system 500 that can record lighting patterns for playback inroom 400 of FIG. 4. Recording system 500 includes multiple “camcorders”510, 520, and 530 that are pointed in different directions. For example,camcorder 520 can be pointed directly up at the sky, while camcorders510 and 530 are pointed in selected compass directions and at angles tovertical. The orientations of camcorders 510 to 530 could alternativelybe selected according to the locations of luminaires in a specificlighting system, such as lighting system 400 of FIG. 4. Conventionalcolor camcorders have only three channels (red, green, and blue), whichis generally inadequate for full spectral recording desired here.Accordingly, each camcorder 510, 520, and 530 is preferably ablack-and-white camcorder in which each pixel sensor is sensitive tolight within a broad spectrum. Camcorders 510, 520, and 530 can berespectively equipped with collimator and prisms, diffraction gratings,or other optical elements 515, 525, and 535 that spatially separatelight having different wavelengths. As a result, a given region of thespectrum, for example, light with wavelengths from 350 nm to 750 nm, isspread out over the surface of the sensor array in each camcorder 510,520, or 530. Once pixel sensors in the camcorder are correlated to theangles over which different wavelengths of light are spread, the amountof light of a particular wavelength can be read directly from theintensity measured by the pixel sensor or sensors at a positioncorresponding to that wavelength.

A data recorder 550 such as a computer with software or a hardwiredsystem can determine intensities in a set of wavelength bands and storethe measured intensities in an illumination data file format thatretains associated spectral, time, and spatial information. The framerate employed for such recording in general will depend on the timescale of the lighting effect recorded. For example, a very low framerate, e.g., less than about once per minute, may be suitable forrecording a day long evolution of outdoor lighting, although a fasterframe rate, e.g., 10 frames per second could be employed at sunrise orsunset or to record the lighting while a storm coming. On the otherhand, lightning can travel at 60 km/s, so a capture rate of 1000 framesper second may be needed for a high fidelity recording of theillumination from a lightning strike.

Instead of black-and-white camcorders with color filters, hyperspectralcameras could be used for recording the spectral and spatial evolutionof lighting. Hyperspectral cameras essentially have a spectrometer ateach pixel and often have many fewer pixels than do video or digitalstill cameras. Hyperspectral cameras are well-known and used inapplications such as remote sensing of the earth for military andenvironmental purposes and industrial process control. Hyperspectralcameras have the drawbacks of being expensive and generating largeamounts of data, which may not be required to record lighting withsuitable fidelity.

Processing of raw illumination data can make the illumination data moreuseful or interesting as input to a lighting system and allow convenientinteraction by lighting designers, artists, and researchers. Forexample, in many cases, the original lighting information, such as a dayof sunlight, changes very slowly, and the slow variation in lightingallows significant compression without loss of useful information. Itmay also be desirable to manipulate or combine recorded scenes. Forexample, a recording of a single candle flame could be overlaid multipletimes to produce the appearance of multiple independent candles, or theintensity and spectral distribution of the candle flame can be alteredto mimic the natural candle's correlated change in color temperature orto hold color temperature constant and only change the intensity. Otherexamples of alterations include morphing different independentlyrecorded lighting patterns smoothly into others to form a new uniquelighting pattern. Light from a sunny day could, for example, transitiontoward rain, then lightning. These transitions could include spectral,spatial, and temporal information.

Another aspect of the processing of the raw files would be to transformspatial or spectral information from the original recording to theactual positions and capabilities of the lights in a room. Lights wouldnot need to be located on a grid or any specific configuration. Insteadany location from grid to unique fixed locations to organic placement(simulate light through tree branches) could be chosen, and the recordedlighting data can be preprocessed or transformed for uses with theexisting luminaires and in area lighting systems.

Other options for processing illumination data include temporalfiltering or insertion. For example, actual illumination data can beaveraged to minimize the effects of fleeting phenomenon such as clouds,sunrise, sunset, or the flickering of a flame. Alternatively, suchtemporary phenomenon may appear at choreographed times or be randomlyinserted over a base lighting pattern representing more constantlighting such as light from a blue sky or the orange or blue body of aflame.

An author, as noted above, may alter recorded illumination data tocreate lighting that is pleasing artistically or achieves the author'sintended effects. However, an author may alternatively create wholly newillumination data without reliance on any recorded lighting data.Similarly, a technician might also create illumination data to create aparticular useful function or result such as optimizing the response ofa biological system to lighting.

Luminaire 200 of FIG. 2 or playback system 450 in FIG. 4 may includedata storage or ports for removable media such as optical disks orelectronic memory that stores a variety of different lighting patterns.“Play lists” could thus be generated to allow a choice of scenes toilluminate a room or other area. For example, a version of “daylight”could be displayed any time as could candle light. However, specificlighting may be more appropriate at specific times, perhaps candlelighting at dinner time and apparent sun light at others. Lightingsystems could create a sunrise on the “east” ceiling transitioningthrough the day to sunset on the “west” ceiling. The “north” sky and“south” sky could also be represented on any part the ceiling or wallthat was desired, and events such as lightning strikes and northernlights could be added for entertainment as well as useful illumination.In addition to functional or entertaining illumination, researchsequences such as circadian rhythm studies could be created and includedin a play list of the lighting system. Such play lists could be madeavailable to others with similar interests and may be commerciallymarketed in the same manner music CDs, video disks, and MP3s and otherdigital entertainment available over the Internet.

Illumination data files that are useful and in desirable formats will ingeneral require skill to create in a similar manner to creating music.Accordingly, illumination data could be subject to legal protection as awork of authorship and may be licensed or transferred commercially. FIG.6 is a flow diagram of a business method 600 employing the legalfeatures of authored illumination data. The business method 600 startswith a step 610 of creating of the illumination data. The illuminationdata can be created using the techniques described above includingrecording illumination data from an environment, constructingillumination data from scratch, and combining or altering illuminationdata from either source. Step 620 then collects and stores illuminationdata that is being offered to users. For example, the illumination datacan be stored in a central location such as a web site or could bestored on physical media CD-ROM or DVD-ROM. A fee for a license can thenbe charged as in step 630 for a user to download the illumination datavia a network such as the Internet or as part of a purchase of physicalmedia. The user can then use the illumination data in a lighting systemas indicated in step 640.

Since lighting systems and each luminaire will generally have differentsets of capabilities such as colors and power levels at each color,illumination data can be altered before sale to create a custom filethat plays back correctly on the lighting system for which the file wasintended. The alteration process can use measured characteristics of theluminaires that are recorded at the factory, and stored in the lightingsystem or cataloged by the serial numbers of the lighting systems.Software can in a reasonably straight forward manner convert astandardized illumination data file into a custom file (or files) tocorrectly playback a desired illumiation. The necessary customizationcould be done automatically at download time by entering the serialnumber of the luminaire(s). Alternatively, luminaires can incorporatethe necessary programs and processing power to convert a standardizedillumination data file into the illumination data needed for thespecific characteristics of the luminaire. Another approach would be tomake each luminaire behave in a consistent manner, so that standardillumination data files could be used without alteration.

A complete set of tools to record, create, and playback illuminationscenes as described above can be analogous to tools now available forentertainment industries such as the music, TV, and motion pictureindustries. However, the manipulations and final uses of the systemsdescribed are not limited to entertainment or human consumption. Forexample, in agriculture where artificial light is used, it may bedesirable (to save energy) to remove the portion of the spectrum that isnormally reflected by the plant (green leaf spectrum) and wasted from abiological process point of view. In industrial process control, machinevision systems could benefit from custom spectral lighting to increasespeed and accuracy of the recognition system. Businesses manufacturingcolored materials (e.g., paints, dyes, plastics, and textiles) couldalso benefit from repeatable, custom spectral lighting to improvequality and consistency of their products.

Although the invention has been described with reference to particularembodiments, the description is only an example of the invention'sapplication and should not be taken as a limitation. Various adaptationsand combinations of features of the embodiments disclosed are within thescope of the invention as defined by the following claims.

What is claimed is:
 1. A lighting fixture comprising: a plurality ofemitters, each of the emitters having an emission spectrum that differsfrom the emission spectra of the other emitters; a driver circuitconnected to the emitters; and a controller that calculates drive levelsfor the emitters and informs the driver circuit to apply the drivelevels to the emitters.
 2. The lighting fixture of claim 1, furthercomprising storage containing calibration data that characterizes theemission spectra of the emitters, wherein calculation of the drivelevels by the controller employs the calibration data.
 3. The lightingsystem of claim 1, wherein calculation of drive levels by the controlleremploys an age of the emitters.
 4. The lighting fixture of claim 1,further comprising a temperature sensor, wherein calculation of thedrive levels by the controller employs a measurement from thetemperature sensor.
 5. The lighting fixture of claim 1, whereincalculation of the drive levels by the controller employs anillumination file selected from among a plurality of illumination filesthat respectively represent a plurality of different lighting patterns.6. The lighting fixture of claim 5, further comprising storagecontaining the plurality of illumination files.
 7. The lighting fixtureof claim 5, wherein one or more of the plurality of illumination filesrepresent light having spectral content and time variation adapted to abiological process.
 8. The lighting fixture of claim 7, wherein thebiological process is a human wake-sleep cycle.
 9. The lighting fixtureof claim 7, wherein the biological process is a plant or animallifecycle.
 10. The lighting fixture of claim 5, wherein one or more ofthe plurality of illumination files are tailored specifically for thelighting fixture.
 11. The lighting fixture of claim 5, wherein one ormore of the plurality of the illumination files represent light having aspectral distribution achieved through application of a filter to alight source.
 12. The lighting fixture of claim 5, wherein one or moreof the plurality of illumination files represent lighting recorded in alighting environment.
 13. The system of claim 5, wherein one or more ofthe illumination files are created by an author.
 14. The system of claim5, wherein one or more of the illumination files represent sky light.15. The system of claim 1, wherein the emitters collectively provideillumination that covers wavelengths beyond a visible spectrum.
 16. Alighting fixture comprising: a plurality of emitters, wherein each ofthe emitters has an emission spectrum that differs from the emissionspectra of the other emitters; and a controller that directs theemitters to produce lighting with spectral content and time variationadapted to a biological process.
 17. The lighting fixture of claim 16,wherein the biological process is a human wake-sleep cycle.
 18. Thelighting fixture of claim 16, wherein the biological process is a plantor animal lifecycle.